The present invention relates generally to detection and identification of airborne particles, and, more particularly, to a continuous system for capturing, washing, processing, and analyzing airborne biological particles.
Infectious biological particles such as bacteria and viruses can be transferred from one organism (e.g., a human or animal) to another via an airborne route. For example, biological particles can inadvertently become aerosolized into bioaerosols when a person speaks, coughs, or sneezes or during certain medical and dental procedures that generate particle-containing droplets. Biological particles can also exist, for example, in vaporized water from cooling towers, water faucets, and humidifiers; in agricultural dust; and in other airborne organic materials.
In addition to bioaerosols that are produced inadvertently from common sources, bioaerosols can be generated intentionally. For example, individuals bent on harming others and disrupting society have demonstrated that hazardous biological particles, such as anthrax in micron-sized particles, can be spread in envelopes delivered through the postal system. Such particles can become airborne during processing in postal facilities or when a contaminated envelope is opened. For example, in October 2001, anthrax was discovered in mail processed by the United States Postal Service in Washington, D.C., resulting in serious illness to postal employees and at least two deaths. In October 2001, anthrax was also discovered in the mail room and office buildings of the Unites States Capitol resulting in closure and quarantine of the buildings. Other methods of intentionally distributing and aerosolizing hazardous biological particles include, for example, dispersing particles through ventilation systems or by explosive release.
In order to protect humans and animals from illness caused by inhalation of hazardous bioaerosols, systems to monitor, detect, and identify bioaerosols exist. One commonly used method for monitoring, detecting, and identifying hazardous bioaerosols employs dry filter devices (e.g., air filters) that are manually collected and analyzed using laboratory procedures. The laboratory procedures involve washing the filters using physical agitation, then performing standard laboratory processes (such as centrifuge) to prepare the sample for analysis. Manually collecting and analyzing the filters, however, presents a logistical burden. Moreover, because the collection and analysis systems involve separate components, conventional methods are not well-suited for use in non-laboratory environments. As a result, such systems are not adapted for use by facility security professionals, military forces, and first responders, such as fire fighters, police, emergency medical personnel, and HAZMAT teams, to determine whether a life threatening biohazard is present at locations on-site and in the field.
Although automated collection and identification systems exist, such systems typically employ wet-walled aerosol collectors or similar devices, which require greater amounts of liquid consumables than a dry filter device. For example, wet-walled aerosol collectors and similar devices typically require significant amounts of liquid reagents during a collection cycle in a high temperature environment because the collection fluids evaporate as a result of the high temperature and have to be replenished. Additionally, in low temperature environments, wet-walled aerosol collectors and similar devices require the use of means to prevent the collection fluid or sample air flow from freezing during collection. For example, the collection fluid may be heated. Heating the collection fluid (or employing other means to prevent the collection fluid from freezing), however, imposes additional power requirements on the system.
Another disadvantage of wet-walled aerosol collectors (or similar devices) is that such devices typically have a low retention factor because collected particles re-aerosolize out of the fluid after being collected. As a result, the amount of sample that can be collected over time is reduced.